Grafana Indexing PoC: Adds feature flag and gRPC endpoint (#93356)

* adds Filter gRPC and make protobuf

* adds route for querying the filter gRPC

* wires up Filter gRPC call

* [WIP] index from start

* renames gRPC endpoint to "Search"

* adds /apis/search route into k8s routes. Hacky for now.

* updates readme - wrong casing

* adds feature toggle for unified storage search

* hides US search behind feature flag. Clean up print statements.

* removes indexer - will be added in another PR

* Search: Add API Builder

* adds required method

* implementing UpdateAPIGroupInfo (WIP)

* adds groupversion

* commenting out for now

* remove unneeded code from experimenting and update register.go to match interface required

* namespaces search route

---------

Co-authored-by: leonorfmartins <leonorfmartins@gmail.com>
Co-authored-by: Todd Treece <todd.treece@grafana.com>

pkg/storage/unified/sql/server.go

@@ -27,5 +27,9 @@ func NewResourceServer(db infraDB.DB, cfg *setting.Cfg, features featuremgmt.Fea
 	opts.Diagnostics = store
 	opts.Lifecycle = store
 
+	if features.IsEnabledGlobally(featuremgmt.FlagUnifiedStorageSearch) {
+		opts.Index = resource.NewResourceIndexServer()
+	}
+
 	return resource.NewResourceServer(opts)
 }